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Re: [EnergyPlus_Support] Return Air Setpoint Control Strategy



Please see the second sentence in group controllers in page 1059:

"It should be noted that a controller cannot span a loop manager
boundary (but a Set Point Manager can). Thus, in an air loop, the sensed
node and the controlled device must be in the air loop simulation."

perhaps I am misunderstanding this, but it looks to me that if both the
control node and the coil are located in the air loop (supply side of
the air system), everything will be ok. However, setting the control
node to the Air Loop Inlet Node, the water flow rate on the coil is just
zero.




Michael J. Witte wrote:
> 
> 
> I am not an expert on how the controller module works, so I am not sure
> if that
> statement is accurate. I am not finding that in the I/O manual, would you
> please cite a page number? But it is quite possible that this will not
> work,
> because the controlled node is so far removed from the cooing coil.
> 
> But this only eliminates options 1 and 2. Option 3 should work. Within the
> limits of the minimum setpoint, Option 3 should maintain all of the
> zones at or
> below the thermostat setpoint. If the supply air temperature
> requirements of
> the zones on the system are signficantly different, this may cause
> overcooling
> in some zones. So, this may not be a good solution either.
> 
> Mike
> 
> On 11 Apr 2007 at 16:20, Jose Coutinho wrote:
> 
>> Thanks a lot Mike,
>>
>> However, from the I/O manual, It looks that CONTROL objects that actuate
>> on Air Loop coils can not sense setpoints at nodes that are located
>> downstream after the Zone Equipment subloop. Is this correct? If it is
>> so, solutions 1-3 are not possible to implement. Actually, your first
>> suggestion is exactly what I tried to model on the first hand.
>>
>> Anyway, thanks again for your suggestions. After all, it is always
>> important to realize that we are thinking the right way.
>>
>> Cheers.
>> Jose'
>>
>>
>>
>> Michael J. Witte wrote:
>> >
>> >
>> > This is not a supported control strategy in EnergyPlus, but I will add
>> > it to
>> > the suggested enhancement list.
>> >
>> > Here are some approaches you could try, but I do not know if they
> will work.
>> >
>> > 1. Use SET POINT MANAGER:SCHEDULED to place the desired return air
> control
>> > temperature as a setpoint on the Air Loop Inlet Node. In the
> CONTROLLER:SIMPLE
>> > object for the cooling coil, set the Control_Node to be the Air Loop
> Inlet
>> > Node.
>> >
>> > 2. Same as 1, but use the ZoneEquipGroup Outlet Node instead of the Air
>> > Loop
>> > Inlet Node. These nodes both represent the same physical point in the
>> > system,
>> > but they are updated at different times in the iteration sequence, so
>> > you might
>> > find one to behave better than the other.
>> >
>> > 3. Use SET POINT MANAGER:WARMEST to place a setpoint on the cooling coil
>> > air
>> > outlet node, and set the controller control node to that node. If
> this is a
>> > draw-thru system, then place this setopint at the fan outlet and use
> a SET
>> > POINT MANAGER:MIXED AIR to place an adjusted setpoint at the cooling
> coil air
>> > outlet node.
>> >
>> > 4. Choose the dominant zone on the system and use it to control the
>> > supply air
>> > temperature with SET POINT MANAGER:SINGLE ZONE COOLING.
>> >
>> > Note - whatever approach you use, be sure to set the cooling priority
>> > (in the
>> > ZONE EQUIPMENT LIST) for the DIRECT AIR units to be 1, and the unit
>> > vents to be
>> > cooling priority 2.
>> >
>> > Mike
>> >
>> > On 7 Apr 2007 at 11:31, coutinho301272 wrote:
>> >
>> >> Dear All,
>> >> I have several zones served by a single constant volume AHU (cooling
>> >> only) plus individual cooling unitvents on each zone. The air system
>> >> has cooling prioriry over the UnitVents and provides fresh air.
>> >> UnitVents will complement cooling needs on each zone.
>> >>
>> >> I wonder how can I control water flow rate in the central cooling coil
>> >> based on return air temperature, ie, by setting a target temperature at
>> >> the Air Loop Inlet Node.
>> >>
>> >> Thanks a lot in advance,
>> >> Jose'
>> >>
>> >>
>> >>
>> >>
>> >> The primary EnergyPlus web site is found at:
>> >> http://www.energyplus.gov <http://www.energyplus.gov>
> <http://www.energyplus.gov <http://www.energyplus.gov>>
>> >>
>> >> The group web site is:
>> >> http://groups.yahoo.com/group/EnergyPlus_Support/
> <http://groups.yahoo.com/group/EnergyPlus_Support/>
>> > <http://groups.yahoo.com/group/EnergyPlus_Support/
> <http://groups.yahoo.com/group/EnergyPlus_Support/>>
>> >>
>> >> Attachments are not allowed -- please post any files to the
>> > appropriate folder
>> >> in the Files area of the Support Web Site.
>> >>
>> >> EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf
> under the
>> >> Documentation link and press the "search" button.
>> >>
>> >> Yahoo! Groups Links
>> >>
>> >>
>> >>
>> >>
>> >>
>> >
>> > ========================================================
>> > Michael J. Witte, GARD Analytics, Inc.
>> > EnergyPlus Testing and Support
>> > EnergyPlus-Support@xxxxxxxx <mailto:EnergyPlus-Support%40gard.com>
> <mailto:EnergyPlus-Support%40gard.com>
>> >
>> >
>>
>>
>> The primary EnergyPlus web site is found at:
>> http://www.energyplus.gov <http://www.energyplus.gov>
>>
>> The group web site is:
>> http://groups.yahoo.com/group/EnergyPlus_Support/
> <http://groups.yahoo.com/group/EnergyPlus_Support/>
>>
>> Attachments are not allowed -- please post any files to the
> appropriate folder
>> in the Files area of the Support Web Site.
>>
>> EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the
>> Documentation link and press the "search" button.
>>
>> Yahoo! Groups Links
>>
>>
>>
>>
>>
> 
> ========================================================
> Michael J. Witte, GARD Analytics, Inc.
> EnergyPlus Testing and Support
> EnergyPlus-Support@xxxxxxxx <mailto:EnergyPlus-Support%40gard.com>
> 
> 


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